There are many applications where water based systems would be cheaper than, and safer to use, than materials currently employed based on organic solvents. Much work has been done in this field and one such development is described in EP-B-No. 0035353 (U.S. Pat. No. 4,339,370) which is directed mainly towards ceramic tile adhesives.
That prior art specification discloses the use of an emulsion copolymer made from at least one vinyl aromatic monomer, at least one (meth) acrylate ester and a minor percentage of an unsaturated organic acid combined with zinc ammonium carbonate and large amounts of inorganic fillers.
Whilst such compositions give ceramic tile adhesives with excellent properties they are more expensive than other copolymer emulsions especially when compositions are required which have some flexibility.
Monomers that are low in cost include vinyl acetate, butadiene and ethylene but not all these give copolymers with the desired properties. For example copolymer emulsions made from vinyl acetate and a minor amount of acrylic acid are unstable in the presence of zinc ammonium carbonate and are difficult to compound into storage-stable form.
Emulsions of the type claimed in EP-B-No. 0035353 can be made more flexible by the incorporation of higher (meth) acrylate esters but this increases the cost.